Optimized Design And Variable Operating Condition Analysis Of The Intake Duct Of Pump-jet Propulsion System

Underwater pump-jet system is a new type of special power propulsion device.Compared with underwater propulsion equipment with large side-screw propeller,the underwater propulsion equipment with pump-jet propulsion has less shallow water effect,low attached resistance and efficiency and higher characteristics.With the layout of the marine power strategy,high-end aeronautical bodies(torpedoes,ships,etc.)have increasing demands for pump spraying above 1300 specific speeds(continuous operation limit line of jet pumps).High specific speed pump-jet propulsion system is necessary for effective hydraulic design and development.In this study,a high specific speed pump-jet system model has been adopted for the underwater vehicle,with a specific speed of 2300,which is about 3 times higher than that of the traditional underwater pump-jet system.Considering the fit between components,the water needs to be introduced into the pump-jet system by circumferentially symmetrical intake ducts.In this paper,a full three-dimensional multi-objective optimization design module suitable for the intake duct of the pump-jet system has been established,so that it can meet the varying performance of different inflow speeds and depths.In this paper,a new type of intake duct with six circumferentially symmetrically arranged diverter blades has been designed and compared on the basis of the traditional round tube intake duct and improved.For a high specific speed underwater pump-jet system,the efficiency and noise of the whole machine often have a close relationship with the intake duct efficiently.This new intake duct can effectively avoid the disadvantage of high uniformity and poor stability of traditional round tube intake duct outlet.It's non-uniformity is 9.33%,which has been reduced by 62% compared with the traditional intake ductA single-component isolation method and a multi-objective optimization design module for the whole machine have been established.The influence of the geometric parameters of the splitter blades(including the leading edge elliptic ratio,leading edge thickness,length,and leading edge sweep angle)on the hydraulic performance of the intake duct has been studied.Among them,multi-objective optimization performs parametric modeling of the intake duct based on the defined geometric parameters,builds a parametric blade modeling program module,and uses the DOE method to perform the overall multi-objective optimization of the intake duct..The hydraulic performance of the runner has been qualitatively and quantitatively evaluated by six indexes of references including outlet flow separation degree,vorticity,outlet unevenness,flow coefficient and total pressure loss coefficient.And Two best hydraulic performance models are designed by the two methods respectively.The CFD software has been used to numerically simulate the inner flow fields in the two modules,and compared with the initial model,the intake duct with the best hydraulic performance and hydrodynamic performance were screened.Finally,the pump-jet system has been analyzed under variable working conditions with different rotor speeds.The results show that the optimization model can effectively suppress the generation and flow separation of the blade leading edge vortex,improve the comprehensive hydraulic performance of the intake duct and the hydraulic efficiency and head of the pump-jet system,and provide theoretical guidance for the optimal design of the intake duct.